Densification and Grain Growth of Nanocrystalline 3Y-TZP Powder Compacts During Two-Step Sintering

Two-step sintering (TSS) was applied on nanocrystalline yttria stabilized tetragonal zirconia (3Y-TZP) to control the accelerated grain growth during the last stage of sintering. The process involves firing at a high temperature (T1) followed by rapidly cooling to a lower temperature (T2) and soaking for a prolonged time (t). It was shown that for nanocrystalline 3Y-TZP (27 nm) the optimum processing condition is T1=1300 °C, T2=1150 °C and t=30 h. In this case, the grain growth is significantly retarded. And grain size of 127 nm is obtained by TSS compared with 260 nm in single-step sintering. It was also found that the density of the compacts must reach to 83% of the theoretical density in first step (sintering at high temperature) to make pores unstable for the further densification at lower temperature.

Keywords:

Tetragonal stabilized zirconia , Densification , Grain growth , Two-step sintering